FIG. 1 shows a sectional view of a portion of a conventional large conveyor, generally indicated 10, which is typically used in mining operations. A set of idlers or upper rollers is carried by a frame 14 and include outer rollers 12 and a central roller 12′. The rollers 12, 12′ rotate with respect to the moving, endless belt 16 that carries the material 18. The rollers 12, 12′ are provided to ensure that the belt 16 defines a trough for the material 18. A plurality of sets of the rollers is spaced to support the belt 16 along the length of the conveyor 10. Lower rollers 20 support the returning portion of the belt 16′.
There is wear and abrasion on the belt 16 caused by slip, friction, material movement, static and dynamic pulling forces, and environmental conditions. Additionally, the belt 16 may be damaged by misalignment, and by foreign material. A downtime due to belt failure may cause significant production losses. Therefore it is important to detect problems before they cause larger belt damage. Typical indications of upcoming belt failures are small cracks at the edges and at the underside where it bends to trough shape.
Furthermore, failure of the idlers or rollers 12, 12′ and their roller bearings causes friction and abrasion. The bearings fail with increasing temperature. A typical lifetime specification of a bearing at 70° C. is 22600 h, but this drops dramatically at higher temperatures (5600 h at 100° C., 2200 h at 120° C.). Factors that cause temperature increase are e.g., quality of manufacturing and assembly, rotation speed, radial load from belt, distance between idlers, grease viscosity, seal, handling and storage of idlers. Typical criteria for replacing idlers are: take note at 70° C., plan replacement at 80° C., and replace above 90° C.
Currently, conveyors are inspected periodically by personnel walking or driving along the length of the conveyor and visually checking for problems. Some inspection crews use thermal cameras to detect the hot spots of failing rollers and roller bearings. Alternatively, conventional automatic inspection systems are usually fixed installations above the belt that measure belt thickness, misalignment or rips at the belt edges. These systems cannot inspect the rollers since the required sensors would be too expensive in that it would not be cost-effective to fix many sensors along the length of the conveyor. Still further, maintenance trolley systems are used that hang from the conveyor. However, since these systems are connected to the conveyor, they are not readily adaptable for use on different conveyors.
Thus, there is a need to provide an unmanned vehicle that is travels adjacent to the operating conveyor to inspect the conveyor. There is also a need to provide a sensor structure that travels adjacent to the operating conveyor in a guided manner to inspect the conveyor.